This invention relates to a solenoid valve device especially suitable for a brake hydraulic control system for a motor vehicle.
A traditional attempt is made in order to reduce a commonly known noise created in a brake fluid channel in brake hydraulic control system during braking of a vehicle. In that attempt, a solenoid valve is configured with a switching valve which can be opened or closed by differential pressure between before and after the solenoid valve. The occurrence of a differential pressure closes the switching valve thereby activating an orifice channel when releasing the solenoid valve.
In that type of solenoid valve, since an orifice channel is located closer to a wheel cylinder side than the solenoid valve is flow velocity through the solenoid valve, which has a channel area wider than the orifice channel, is higher than flow velocity through the orifice channel. Accordingly, higher hydraulic pressure at the master cylinder side of the solenoid valve delays the closing of the solenoid valve or prevents the sufficient closing of the solenoid valve.
An object of this invention is to provide a solenoid valve device which makes the reduction of the above-mentioned noise and its normal opening and closing operation possible.
A further object of this invention is to provide a solenoid valve device which makes an accurate switching valve operation possible.
In the first aspect of the invention, a solenoid valve device, installed in a brake fluid channel between a master cylinder and a wheel cylinder, comprises a master cylinder port connected to a channel located at the master cylinder side, a wheel cylinder port connected to a channel located at the wheel cylinder side, a hydraulic chamber connected to a high-resistance duct and the master cylinder port, a switching valve activated due to a hydraulic pressure difference between the hydraulic chamber and the wheel cylinder port to form an orifice; and a solenoid valve, installed in a channel connecting a switching valve and the wheel cylinder port, which opens or closes the channel by application of an electromagnetic force.
In the second aspect of this invention, a solenoid valve device as above further comprises a piston which is capable of stroking due to hydraulic pressure of the hydraulic chamber and the wheel cylinder port and a piston spring urging the piston toward the hydraulic chamber side; wherein an orifice is formed upon an upward piston stroke sliding away from the hydraulic chamber side to operate the switching valve.
In the third aspect of the invention, a solenoid valve device as above further comprises a nozzle extending into the piston and a hydraulic supply opening connected to the hydraulic chamber between the nozzle and the piston.
In the fourth aspect of the invention, a solenoid valve device as above further comprises a valve housing inside which the piston is housed to form the hydraulic chamber with the piston and a hydraulic supply duct which is formed between the valve housing and the piston and connects the hydraulic chamber and the hydraulic supply opening.
In the fifth aspect of the invention, a solenoid valve device as above further comprises a relief channel bypassing the solenoid valve and the switching valve.